The majority of the deaths associated with breast cancer are caused by the primary tumor metastasizing to distant organ sites. Metastasis is a very complex sequence of molecular and cellular events. A cellular program named epithelial-mesenchymal transition (EMT) is shown to be vital process in initiating dissemination of primary tumor cells to form metastatic lesions. The basic helix-loop-helix (bHLH) transcription factor, Twist, is highly up-regulated in invasive breast tumors and plays a key role in initiating EMT. To determine the downstream transcriptional network of Twist-mediated EMT and metastasis, the following specific aims will be investigated: 1. Define the transcriptional target genes that are under the direct control of Twist. Twist will be activated in human mammary epithelial cells and chromatin immunoprecipitation (ChIP) coupled with high throughput sequencing will identify the direct binding targets of Twist, 2. Determine the functional role and biological significance of Twist target genes in EMT and metastasis. Using the identified Twist target genes from aim 1, shRNAs will be made to the top candidate genes and knockdown experiments will be performed in in vitro models and changes in protein expression will be observed. Effective shRNAs will be translated into in vivo mouse models to determine the gene requirement in tumor metastasis. 3. Examine the involvement of Twist target genes in human breast cancer. An analysis of published sets of breast cancer gene expression profiles will be analyzed to determine whether more aggressive tumors express Twist and its target genes. Immunohistochemistry for Twist and its target genes will be performed on human cancer samples to determine whether Twist and its direct target genes can serve as prognostic markers PUBLIC HEALTH RELEVANCE: Metastatic lesions are the primary cause of mortality in cancer patients. Studying the key protein involved in cancer metastasis. Twist, will provide a better understanding of how metastasis happens and potentially identify novel targets for cancer therapies and act as prognostic markers for more aggressive cancers.